Heat exchanger



Jan. 16, 1968 J F, Ev oc ET AL 3,363,681

HEAT EXCHANGER Original Filed Nov. 10, 1964 s Sheets-Sheet 1 LN E i T :i-

HOT FLUE GAS J2 f A 45 cow 4/? COLD All? COLD FLUE GAS INVENTORS r0 STACK A I F,

JOSEPH E REVILOCK SAMUEL H.S. RAUB ATTORNEY Jan. 16, 1968 EVI OCK ET AL HEAT EXCHANGER m 5 B J R P m WW VRS & WEH E h EU S SM 3 0A ds Original Filed Nov. 10, 1964 A 7' TORNE V Jan. 16, 1968 F REVILOCK ET AL 3,363,681

HEAT EXCHANG ER 3 Sheets-Sheet 5 Original Filed Nov. 10, 1964 INVENTORS JOSEPH F REVILOCK SAMUEL H. 5. RAUB ATTORNEY United States Patent 3,363,681 HEAT EXCHANGER Joseph F. Revilock, Tuckahoe, N.Y., and Samuel H. S. Raub, Bay Village, ()hio, assignors to Union Carbide Corporation, a corporation of New York Continuation of application Ser. No. 410,107, Nov. 10, 1964. This application Jan. 24, 1967, Ser. No. 611,469 7 Claims. (Cl. 165-166) This is a continuation of application Ser. No. 410,107, filed Nov. 10, 1964, now abandoned.

This invention relates, in general, to heat exchangers and in particular, to line gas heat exchangers of the plate pack type in which plate-shaped heat transferring walls of thin plate material are arranged in pallet-shaped module units serving as passages for fluid media.

Heretofore, in the recovery of heat from flue gases using air preheaters it was not feasible from the standpoint of heat exchanger costs and overall efficiency to cool flue gases below 325 F. Since water as one of the products of combustion tends to combine with sulphur dioxide and with other of the products of combustion to form highly corrosive dilute acids such as sulfurous acid any preheater operating at the low temperatures employed in a boiler would corrode and abrade unless it was composed of a corrosion resistant material, such as graphite. Although the use of graphite eliminates the corrosion problem, most prior tube designs were unsuccessful in justifying the further cooling of flue gases below 325 F. because of high pressure drops which contributed to lower boiler efiiciences.

It is therefore that principal object of the invention to provide means for obviating these and other disadvantages of such prior art heat exchangers.

It is another object of the invention to provide a highly economical, efiicient and relatively simple heat exchanger which can be inexpensively manufactured and sold at a relatively reduced price.

Yet a further object of the invention is to provide a structure of pallet-shaped module units which can be readily assembled horizontally or vertically so that either counter-flow or cross-flow heat transfer can occur.

The individual unit cell structure or palleted-shaped module unit according to the invention comprises two opposing, parallel, thin-plate members of a carbonaceous material such as graphite, spaced fixedly apart from each other by a plurality of spacing elements.

The invention will now be described more in detail with reference to the accompanying drawing which illustrates preferred embodiments of the invention, and in which:

FIGURE 1 is a side elevational view of a heat exchanger comprising module units according to the invention;

FIGURE 2 is a transverse section view taken along the line 2-2 of FIG. 1;

FIGURE 3 shows a section taken along the line 3-3 of FIG. 1 and showing on an enlarged scale the lower portion of the heat exchanger;

FIGURE 4 is another enlarged sectional view taken along line 4-4 of FIGURE 1 and showing the uppermost connecting joints;

FIGURE 5 is greatly enlarged fragmentary view illustrating a typical connecting joint or seal between adjacent plates of adjacent module units;

FIGURE 6 is a perspective view on an enlarged scale, and partly in section of a module unit of the invention;

with the interspaces between the walls FIGURE 7 is a perspective View, in section, of the top portion of the heat exchanger;

FIGURE 8 is a perspective view, on an enlarged scale plurality of module units arranged for use in a horizontal-type heat exchanger; and

FIGURE 9 is another perspective view, partially broken away, of a horizontally disposed heat exchanger employing the module units of the invention as shown in the arrangement of FIG. 8.

Referring to the drawings, and particular to FIGURES l7, a single-pass heat exchanger 10 is shown therein comprising a plurality of unit cells of a pallet-shaped construction. The individual unit cell or module unit 12 is best shown in FIG. 6 and comprises a pair of thin slabs 14 and 16, suitably of graphite, separated from each other in parallel by a pair of side edge plates 18 and 20 and a plurality of spacers 22. The edge plates 18 and 20 and the spacers 22 are preferably secured to the slabs 14 and 16 by means of an adhesive such as a resin or carbonaceous cement or by other suitable fastening means conventionally used in the art, such as pins. It should be apparent that the relatively large heat transfer area of each module unit, coupled with an inherently low pressure drop offered by such construction is not attainable in conventional designs employing circular-section graphite tubes of practicable size. To match the low pressure drop attainable with such pallet-shaped construction using circular-section graphite tubes, the cross-sectional flow area with the gas flowing through the tubes would have to be increased greatly which would result in an unnecessary increase in heat transfer area. Since the cost of heat transfer area of circular-section graphite tubes is much greater than that of the pallet-shape construction, the economic justification to recover additional heat at line gas temperatures below 325 F. becomes less attractive.

This type of module unit 12 is to be noted to be provided with top and bottom openings, (numerals 18 and 20 representing the side edge plates).

In the particular heat exchanger shown in FIG. 1 twenty four modules 12 are required for each box section 24 and there are six box sections, one atop the other. The lowermost box section 26 is slightly different from the other box sections 24 in that it is disposed atop a support frame 28 and is provided with a side opening (not shown) communicating with an outlet cold air duct nozzle 30. Within the support frame 28 which is supported on a suitable foundation 32., a refractory brick base wall 34 is provided beneath the lowermost box section 26 so that any fiue dust or fly ash can accumulate on the foundation and be periodically removed therefrom. As best shown in FIG. 3, entrance into the interior side of the brick wall is provided for by a covered man hole 36 which is located in the side wall thereof. The cold flue gas exiting from the heat exchanger 10 leaves by means of the exit port 38 which is also provided in the side wall of the base wall 34.

Suitable supporting beams 40 are provided across the base wall 34 for supporting the box sections 26 and 24 of the heat exchanger 10. Each box section 24 is comprised of a top and bottom angle iron frame 42 and 44 respectively and a plurality of U-shaped spacers 46, suitably welded thereto at their tops and bottoms opposite each other and between each module unit 12. These U- shaped spacers 46 align and guide the location of the module units 12. The (four) outer walls 43 of each box section 24 and 25 are suitably of thin plate stock such as A" steel plate. Box sections 26, as shown in FIG. 2, differs slightly from box section 24 (not shown) in that U-shaped spacers 46 are provided on one side and retaining channels 47 on the other side but indexed or displaced adjacently by about one module unit thickness. This is to enable the cold air to enter from duct nozzle 3%} via the side opening in box section 26 to the cold air spaced openings between adjacent module units 12. It should be obvious that the space between the thin slabs 14 and 16 of each module unit 12 is for the flow of corrosive fluid media; thus the outermost spaced openings contain cold air since one side thereof is formed by the walls 48 which are generally of steel plate.

At each module joint 55%} except for the uppermost joint 52, a suitable rope or O-ring type of seal 54 is provided between the adjacent slabs l4 and 16. FIG. is a greatly enlarged sectional view of such a seal 54.

The top joint seals 56 and the separator assembly 58 will not be described in detail with particular reference to FIGS. 1, 4, and 7. The separator assembly 58 connects the uppermost box section 24 to the hot flue gas inlet nozzle 60 and the warm air exit nozzle 62 and is suitable constructed of steel and the like. The separator assembly 58 is made in a box-like construction form. As best shown in FIG. 1, the bottom portion of the separator assembly 58 is composed of a suitable angle iron frame $54 which communicates with the top frame 4-2 of the uppermost box section 24. As shown in FIGS. 4 and 7, grommet like joint seals 56 are preferably employed to seal the space between the slabs 1d and I6 and the separator plates 66. A pair of adjacent separator plates as closed at the curved portion 68 form a passageway 76 which either leads to the left (to the warm air exit nozzle 62) or to the right (to the hot flue gas inlet nozzle 60) when viewing FIG- URE 1. It should be noted at this time that the separator plates 66 save for the two end separator plates 72 (only one shown) are actually in the form of a V-block with convex V surfaces, whereas the end separator plates 72 resemble a quadrant of a circle. Thus, there is no double wall construction at points 74 which would lend itself to higher costs and to more difficult sealing problems. Of course, suitable angle iron frames 76 and 78 of the separator assembly 58 are respectively connected to the warm air exit nozzle 62 and the hot flue gas inlet nozzle 60.

As indicated above in the operation of the heat exchanger of the invention as shown in FIG. 3, the fluid media which is to be heated flows upwardly through the passageways 80 formed between adjacent module units 12 and the heating fluid media flows opposite thereto (counterflow) or downwardly through the passageway 82 formed by the module units 12.

FIGURES 8 and 9 illustrate a modified form of the invention in that a single pass heat exchanger 84 is disposed horizontally rather than vertically. In this construction, all of the module units 12 are arranged in one direction and the cold-air passageways 86 are similarly arranged such that the fluids flowing therethrough are at substantially right angles with each other (cross-bore flow conditions). In FIGURE 9, hot flue gas enters duct 88 and is distributed along the length of the exchanger E54 by means of a common inlet manifold 90. The cooler flue gas exits via exit manifold 92 and exit duct 94. In a similar manner cold air enters duct 96 and associated manifold (not shown) and leaves as hot air by exit manifold 98 and exit duet 100.

It should be noted that many other modifications and changes in the construction and arrangement of the parts may be made without departing from the spirit and scope of the invention and therefore it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense. If desired, for example, the module units can be arranged in the heat exchanger so that multiple passes can be made by directing the fluid sinuously through the passageways. Also, baffles may be employed within each module unit to vary the fluid flow pattern.

We claim:

l. A heat exchanger, comprising:

(a) a casing having inlet means and outlet means for two different fluids which are to undergo heat exchange in said heat exchanger;

(b) a plurality of box sections each comprising a first angle iron frame, a second angle iron frame, and a plurality of spacers secured to said first and second frames, said spacers on each frame being placed on opposite sides of said frame and in a pair relationship, said box sections being positioned adjacent each other;

(c) a plurality of unit graphite cells, said cells comprising a pair of thin slabs separated by a pair of side edge plates and a plurality of spacers, the edge plates and the spacers being secured to the slabs, each of said unit cells being positioned in said box sections and being aligned and separated by said spacers on said frames, one of said fluids flowing from one of said inlet means through said unit cells to said outlet means, and the other of said fluids flowing through the space between said unit cells to said second outlet means whereby said fluids undergo heat exchange.

2. The heat exchanger of claim 1 wherein said box sections are stacked end to end such that said unit cells form vertical flow lanes for said first fluid, and the space between said unit cells form vertical flow lanes for said second fluid.

3. A heat exchanger having a casing with inlet and outlet means for two different fluids which are to undergo heat exchange, comprising:

(a) a plurality of unit cells, said cells comprising a pair of thin carbonaceous slabs separated by a pair of carbonaceous side edge plates and a plurality of spacers, said slabs being substantially parallel to each other, said edge plates and said spacers being secured to the slabs;

(b) means for separately securing said unit cells in said heat exchanger, said unit cells being positioned to form a plurality of columns spaced apart from each other, said first fluid flowing through said unit cells, and said second fluid flowing through the space between said unit cells whereby said fluids undergo heat exchange.

4. The heat exchanger of claim 3 wherein said slabs and said side plates of said unit cell are composed of graphite.

5. A heat exchanger, comprising:

(a) a casing having inlet means and outlet means for two different fluids which are to undergo heat exchange;

(b) a plurality of box sections positioned adjacent each other, said box sections being in communication with each other, and

(c) a plurality of unit graphite cells, said cells comprising a pair of thin slabs separated by a pair of side edge plates, said edge plates being secured to said slabs, said unit cells being positioned and aligned in said box sections so as to form flow lanes through said cells for one fluid and between said cells for the other fluid to thereby cause heat exchange between said fluids.

6. The heat exchanger of claim 5 wherein a separator assembly connects the end box section to said inlet means, said separator assembly comprising:

(a) two end separator plates having a configuration approximately equivalent to a quadrant of a circle;

(b) a plurality of adjacent separator plates between said end plates, each adjacent pair of separator plates defining a passagweay for said fluids, alternate passageways having openings approximately apart whereby said fluids which are to undergo heat exchange are precluded from contacting each other upon entering the heat exchanger.

5 7. The heat exchanger of claim 6 wherein said separator plates between said end separator plates are in the form of a V-block with movex V surfaces whereby only one of said separator plates forms a common wall between at least a portion of adjacent passageways.

References Cited UNITED STATES PATENTS 3,044,861 7/1962 Hasche 23-277 6 3,055,789 9/1962 Gemmi 156327 3,183,960 5/1965 Prat 263-19 X 3,187,502 6/1965 Stover 138155 3,231,015 1/1966 Koch 165166 X FOREIGN PATENTS 580,632 4/1924 France. 725,332 2/1932 France.

ROBERT A. OLEARY, Primary Examiner. T. W. STREULE, Assistant Examiner. 

1. A HEAT EXCHANGER, COMPRISING: (A) A CASING HAVING INLET MEANS AND OUTLET MEANS FOR TWO DIFFERENT FLUIDS WHICH ARE TO UNDERGO HEAT EXCHANGE IN SAID HEAT EXCHANGER; (B) A PLURALITY OF BOX SECTIONS EACH COMPRISING A FIRST ANGLE IRON FRAME, A SECOND ANGLE IRON FRAME, AND A PLURALITY OF SPACERS SECURED TO SAID FIRST AND SECOND FRAMES, SAID SPACERS ON EACH FRAME BEING PLACED ON OPPOSITE SIDES OF SAID FRAME AND IN A PAIR RELATIONSHIP, SAID BOX SECTIONS BEING POSITIONED ADJACENT EACH OTHER; (C) A PLURALITY OF UNIT GRAPHITE CELLS, SAID CELLS COMPRISING A PAIR OF THIN SLABS SEPARATED BY A PAIR OF SIDE EDGE PLATES AND A PLURALITY OF SPACERS, THE EDGE PLATES AND THE SPACERS BEING SECURED TO THE SLABS, EACH OF SAID UNIT CELLS BEING POSITIONED IN SAID BOX SECTIONS AND BEING ALIGNED AND SEPARATED BY SAID SPACERS ON SAID FRAMES, ONE OF SAID FLUIDS FLOWING FROM ONE OF SAID INLET MEANS THROUGH SAID UNIT CELLS TO SAID OUTLET MEANS, AND THE OTHER OF SAID FLUIDS FLOWING THROUGH THE SPACE BETWEEN SAID UNIT CELLS TO SAID SECOND OUTLET MEANS WHEREBY SAID FLUIDS UNDERGO HEAT EXCHANGE. 